US prosecutors believe FIFA President Sepp Blatter's top lieutenant made $US10 million in bank transactions that are central to the bribery investigation of the world football body, a source familiar with the matter said on Monday.
Jerome Valcke, FIFA's secretary general, is described in an indictment filed in federal court in Brooklyn, New York, as an unidentified "high-ranking FIFA official" who in 2008 transferred the sum to another FIFA official, Jack Warner.
Mr Valcke is not named as a defendant and has not been accused of any wrongdoing. He was not immediately available for comment.
Mr Valcke and Mr Blatter are the top two officials within FIFA. His connection to the case was first reported by The New York Times, which said Mr Valcke had said in an email to the newspaper that he had not authorized the payment nor had the power to do so.
After news broke of his alleged connection to the case, FIFA announced that Mr Valcke would not attend the opening of the FIFA Women's World Cup Canada 2015 due to begin 6 June as previously scheduled.
"It is important that he attends to matters at FIFA's headquarters in Zurich," FIFA said in a statement.
Mr Warner, a former FIFA vice president, is among 14 FIFA officials and corporate executives charged by the US Department of Justice last Wednesday with running a criminal enterprise that involved more than $US150 million in bribes.
The $US10 million payment is featured in the indictment accusing Mr Warner, who was among those charged, of taking a bribe in exchange for helping South Africa secure the right to host the 2010 World Cup.